Field of the Invention
The invention lies in the field of oil pumps, preferably in the field of electrically operated or driven oil pumps, and relates to an oil pump of said type. An oil pump can be, for example, a main pump and/or an additional or auxiliary pump in or for a motor vehicle.
Description of the Background Art
An electric oil pump typically serves for delivering oil as lubricant for in particular moving parts or components, for example also of a vehicle (motor vehicle) driven by internal combustion engine, by hybrid technology or electrically. An oil pump of said type normally generates, owing to its delivery characteristics, an oil circuit, for example with an oil sump for accommodating excess oil and/or leakage oil.
Oil pumps of said type must be configured, or structurally designed, for relatively large temperature ranges. The temperature range that must be managed or allowed typically lies between −40° C. and 130° C. Here, it must also be taken into consideration that the lubricant (oil) that is used exhibits a certain or particular viscosity, which is temperature-dependent and which decreases with increasing temperature, that is to say is greater at low temperatures than at high temperatures.
In a vehicle gearbox, in particular in an automatic gearbox, there are often provided multiple parallel oil circuits with a respectively associated oil pump. Here, a distinction is typically made between one or more main (oil) circuits and one or more auxiliary or additional circuits, wherein a main circuit normally requires an oil pump with a higher volume flow than an auxiliary or additional circuit.
An auxiliary or additional pump, driven for example electrically or by electric motor, often serves for the at least intermittent lubrication or additional lubrication of gearbox parts of the vehicle gearbox. Here, the delivered oil also serves for the cooling of components or additional components of the drivetrain of a vehicle of said type. A main oil pump, which is driven for example electrically or by electric motor, serves, in a main circuit, in particular as an accumulator charging pump for providing a supply to, and for actuating, hydraulic gearbox parts, in particular hydraulic gearbox actuators for the engagement and/or shifting of gearbox ratios.
Pump types that are commonly used for such purposes are for example positive-displacement pumps (external-gearwheel pumps), sickle-cell pumps or vane-type pumps. A relatively inexpensive and in this case relatively pulsation-free pump type is an oil or auxiliary oil pump with a so-called gerotor (G-rotor pump). An oil pump of said type has a rotor set (gearwheel set) with an internally toothed outer ring (outer toothed ring) and an externally toothed inner rotor (inner gearwheel, inner toothed ring).
The prior art discloses, for example, pump units in the form of so-called tandem pumps. Here, by means of a single drive motor, two mutually independent volume flows, in particular for a main circuit and an auxiliary or additional circuit, are generated.
DE 10 2012 111 637 A1 has disclosed, for example, an oil pump for a motor vehicle, in the case of which oil pump two pump rotors formed as external-gearwheel sets are arranged in a common pump housing. The two pump rotors have in each case two intermeshing external gears for oil delivery, wherein the external-gearwheel sets are arranged coaxially one above the other in the pump housing such that in each case one gearwheel is driven by a common drive shaft. In this way, two pump chambers are realized within the pump housing, which pump chambers are arranged coaxially one above the other and are separated by way of a partition, whereby the known oil pump requires a relatively large structural volume.